Frazzled nerves at Daly City flood site

DALY CITY

Updated 1:52 pm, Saturday, November 17, 2012

Up to an inch of rain is expected over the weekend in the area of Daly City that saw a mudslide after a pipe broke Tuesday.

Up to an inch of rain is expected over the weekend in the area of Daly City that saw a mudslide after a pipe broke Tuesday.

Photo: Paul Chinn, The Chronicle

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A grassy field at Hillside Park is still covered with up to four feet of mud next to homes in Daly City, Calif. on Friday, Nov. 16, 2012, three days after a broken water pipe caused a huge mudslide to roll through the neighborhood.

A grassy field at Hillside Park is still covered with up to four feet of mud next to homes in Daly City, Calif. on Friday, Nov. 16, 2012, three days after a broken water pipe caused a huge mudslide to roll

A mud-caked car sits in the driveway of a Bonnie Street home in Daly City three days after a water main broke and sent a mudslide through the area.

A mud-caked car sits in the driveway of a Bonnie Street home in Daly City three days after a water main broke and sent a mudslide through the area.

Photo: Paul Chinn, The Chronicle

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Resident Emee Bautista keeps a watchful eye on the hill above her home in Daly City, Calif. on Friday, Nov. 16, 2012, three days after a broken water pipe caused a huge mudslide to roll through the neighborhood. "I'm scared to leave the house," she said.

A Public Works crew continues to hose down remnants of mud at Hillside Park in Daly City, Calif. on Friday, Nov. 16, 2012, three days after a broken water pipe caused a huge mudslide to roll through the neighborhood.

A Public Works crew continues to hose down remnants of mud at Hillside Park in Daly City, Calif. on Friday, Nov. 16, 2012, three days after a broken water pipe caused a huge mudslide to roll through the

Three days after an aging water main broke and pushed a goopy mudslide through a Daly City neighborhood, the streets are clean but some residents remain anxious about the flood's gaping trench in the hillside above them.

The area is supposed to see up to an inch of rain over the weekend, officials said, and while it's just a sprinkle compared with the 98,000 gallons of water that gushed out of the 8-inch pipe Tuesday, some residents remain uneasy.

"I'm so scared to leave the house," said Emee Bautista, 65, whose house borders Lausanne Avenue, which was turned into a river of mud Tuesday morning. "If that happened again, you never know what'll happen. The earth there (on the hillside) is so soft - something serious could happen. Water is so strong."

Patrick Sweetland, the city's director of water and wastewater resources, said the hillside is safe but he understands the concerns residents have, especially those whose houses were evacuated for several hours until engineering crews deemed the hillside stable.

"For 32 minutes, we had 98,000 gallons in a very limited time in a very confined location coming down the hill," Sweetland said. "We don't anticipate that kind of flow with these rains. But the guy up on Bonnie Street - I get where he's coming from."

A 25-foot segment of the 78-year-old cast iron pipe broke off around 4:18 a.m. Tuesday, spewing water from a 970,000-gallon storage tank on a hill above the neighborhood. Officials initially said about 45,000 gallons of water gushed out but doubled the estimate later in the week.

The washout left a trench about 20 feet wide by 20 feet deep carved into the hillside, and the city estimates it displaced about 3,000 to 5,000 cubic yards of silty brown dirt.

Building engineers declared the hillside stable Tuesday morning, but the fractured hillside is still a striking sight.

"At first I wasn't concerned," said Epifanio Agbayani, 69, who lives on Bonnie Street just below the hill. "But when I walked down and looked up at the big hole I said, 'Wow.' We hope for the best."

Arturo Romero, his neighbor, said he feels the precautions the city has taken - hay bales, netting stretched over Hillside Park - are enough to keep the remaining mud away from the street.

"But I don't think the hill is stable yet," said Romero, 64. "That's a big, big hole. And if the water had gone straight down, our house would have been pushed down the street."

No homes were damaged Tuesday, but a dozen cars were buried in mud up to the tops of the tires. Romero's son's car received bumper and undercarriage damage, he said.

Public works employees cleared the street by 6 p.m. Tuesday, but spent Wednesday and Thursday preparing for weekend showers, Sweetland said. The netting and hay bales should divert any water away from houses, and crews used vacuum trucks to suck and clear mud out of storm drains.

The hill where the water tank burst is part of a group of ancient sand dunes formed around 100,000 years ago, said Ken McIntire, executive director of San Bruno Mountain Watch, a preservation group. The hill has some underlying rock but is mostly old sand with organic matter mixed in. That could account for the large swath of soil that came out when the water main broke, he said.

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